One of the oil well completion techniques used in determining which, if any, completion procedures are to be applied to the well involves taking a cylindrical rock core. Moreover, the rock core can provide additional data which is important to selection of a particular completion technique. It is not uncommon to cut a long cylindrical rock core or core sample from a well at an intermediate stage during drilling. Often, a cutting tool is lowered into the well so that a sample up to several feet in length is obtained. It is typically removed to a laboratory where certain tests are run on the sample. Many measurements can be taken such as permeability, porosity, and the like. In addition, other measurements are taken of physical parameters such as weight and density. After many physical measurements are obtained from the core sample, it is not uncommon to slice the core sample lengthwise to thereby obtain two halves, separated by a diametrical cut, and other inspection techniques may well be practiced on the facing diametrical faces.
For the latter purpose, a saw is normally required to cut through the core sample. The core sample must be held by an alignment tool so that the saw can proceed along the length of the core sample to form the cut. As the cut is made, the resistance of the core sample to cutting will be observed. The present apparatus provides a log of cutting the core sample. This log enables additional analysis to be obtained from the core sample. For instance, it permits plotting of the resistance of the core sample to cutting as the cut is made so that variations along the length of the core sample are noted. This is particularly useful to provide an indication of strength, brittleness, and other factors which relate to the mechanical properties of the core sample.
The present apparatus is thus adapted to be used with a motor driven rock cutting saw blade. Various indicators are measured so that the brittleness, strength, and hardness of the core sample can be determined. The present apparatus includes X, Y and Z vibration sensors which are accelermeters mounted on the motor. Vibration is imparted to the motor from the chatter of the saw blade as it cuts through the core sample. In addition, the motor current is monitored to obtain another output. The motor is advanced during cutting, therebeing a weight mechanism to pull the motor along the core sample, and the tension imparted to the motor is thus also recorded. The position of the motor along the core sample is likewise recorded. A microphone is included at a fixed location relative to the motor to record the sound level during cutting. All of this data is input to a CPU and then to a recorder where it is recorded as a function of time. As will be discussed hereinafter, physical properties of the core sample can be determined after cutting.